A fuel cell is a power generating device using a chemical reaction between stored hydrogen or hydrogen obtained by reforming alcohol or ether etc. and the oxygen in the air to obtain electric power. As typical fuel cells, there are phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), and polymer electrolyte fuel cells (PEFC). Among these fuel cells, polymer electrolyte fuel cells are more suitable for reduction of size compared with the other types. For this reason, polymer electrode fuel cells are perfect for mounting in passenger cars and other transport machinery where there are many restrictions on the installation location.
In the above-mentioned general polymer electrolyte fuel cells (PEFC), separators are arranged at both of the fuel electrode supplying the hydrogen (negative electrode/anode) and the air electrode supplying the oxygen (positive electrode/cathode). A membrane electrode assembly (MEA) is sandwiched between the two separators. This membrane electrode assembly is comprised of a proton conducting membrane at the two sides of which catalyst layers, water repelling layers, and at the outside of the same gas diffusion layers are stacked. Further, the necessary number of combinations of these are connected to form a fuel cell (for example, see PLTs 1 and 2).
As shown by the above-mentioned structure, hydrogen and oxygen are supplied to the membrane electrode assembly. In this case, water and electric power are produced from the hydrogen and oxygen and heat is also generated. If excessive heat is generated inside the cell, it affects the reaction efficiency and becomes a cause for a drop in amount of power generated. Further, it is also liable to obstruct the discharge of water, the reaction product of the fuel, from the fuel cell. Therefore, in a polymer electrolyte fuel cell, along with the supply of hydrogen and oxygen, water or another cooling medium is supplied to predetermined portions inside the cell to stabilize the reaction temperature (similarly see PLTs 1 and 2).
To further raise the cooling effect due to the circulation of a cooling medium, the channels are made finer to increase the surface area of the channels. Further, by forming finer channels, it becomes possible to assemble them inside the membrane electrode assembly or other cell. This being so, it is possible to more efficiently cool the locations where heat is generated inside the cells.
Therefore, the method of preparing a channel member for fuel cell use which secures conductivity, is highly convenient for combination with a separator or membrane electrode assembly of a polymer electrolyte fuel cell, enables formation of finer channels, is suitable for the circulation of hydrogen, oxygen, a cooling medium, or other various fluids, and is inexpensive and easy to produce has been desired.